ALLOYS AND COMPOSITE MATERIALS

 

ALLOYS AND COMPOSITE MATERIALS

 

Department of Mechanical Engineering

MEA-SY

 (01)Aayush Singh  11911345

(11)Rohan Arwari  11910498

  (14)Atharva Yewale  11911264

 (17)Harsh Baheti  11910928

 Instructor: Prof. Rahul Waikar

Course: Mechanical and System Engineering

Date: 07/12/2020

 

 

 

 

 

 

Alloy –

·         An alloy is a combination of metals or metals combined with one or more other elements.

·         An alloy may be a solid solution of metal elements (a single phase, where all metallic grains (crystals) are of the same composition) or a mixture of metallic phases (two or more solutions, forming a microstructure of different crystals within the metal).

 

 

History of Alloy –

Bronze, an alloy of copper and tin, was the first alloy discovered, during the prehistoric period now known as the Bronze Age.

 

Characteristics of Alloy –

·         An alloy is a mixture or metallic solid solution composed of two or more elements.

·         An alloy’s properties are usually different from those of its component elements.

·         Alloy constituents are usually measured by mass.

·         Unlike pure metals, most alloys do not have a single melting point; rather, they have a melting range in which the substance is a mixture of solid and liquid.

·         Examples of alloys include materials such as brass, pewter, phosphor bronze, amalgam, and steel.

·         Complete solid solution alloys give single solid phase microstructure. Partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history. An alloy’s properties are usually different from those of its component elements.

·         Alloy constituents are usually measured by mass.

·         An alloy is usually classified as either substitutional or interstitial, depending on its atomic arrangement.

·         In a substitutional alloy, the atoms from each element can occupy the same sites as their counterpart.

·         In interstitial alloys, the atoms do not occupy the same sites. Alloys can be further classified as homogeneous (consisting of a single phase), heterogeneous (consisting of two or more phases), or intermetallic (where there is no distinct boundary between phases).

·         Unlike pure metals, most alloys do not have a single melting point; rather, they have a melting range in which the substance is a mixture of solid and liquid. However, for most alloys, there is one particular proportion of constituents, known as the “eutectic mixture,” at which the alloy has a unique melting point.

 

How is Alloying Done?

·         Alloying a metal is done by combining it with one or more other elements.

·         The most common and oldest alloying process is performed by heating the base metal beyond its melting point and then dissolving the solutes into the molten liquid, which may be possible even if the melting point of the solute is far greater than that of the base.

·         For example, in its liquid state, titanium is a very strong solvent capable of dissolving most metals and elements. In addition, it readily absorbs gases like oxygen and burns in the presence of nitrogen. This increases the chance of contamination from any contacting surface, and so must be melted in vacuum induction-heating and special, water-cooled, copper crucibles. 

·         However, some metals and solutes, such as iron and carbon, have very high melting-points and were impossible for ancient people to melt. Thus, alloying (in particular, interstitial alloying) may also be performed with one or more constituents in a gaseous state, such as found in a blast furnace to make pig iron (liquid-gas), nitriding, carbonitriding or other forms of case hardening (solid-gas), or the cementation process used to make blister steel (solid-gas).

·         It may also be done with one, more, or all of the constituents in the solid state, such as found in ancient methods of pattern welding (solid-solid), shear steel (solid-solid), or crucible steel production (solid-liquid), mixing the elements via solid-state diffusion.

 

Types of Alloys –

                There are basically four different types of alloys:

·         Aluminium Alloys – Although aluminium alone isn’t the strongest metal, it is used in combination with other metals to create conductive, heat, and tarnish resistant alloys. Aluminium is used in many essential mechanical components including car engines, airplane body panels, and boat hulls.

·         Nickel Alloys – When Nickel and other metals come in contact with specific chemicals, they react in a way that produces electricity. This process has been harnessed in batteries worldwide and continuing research in the field has led to the promise of electric cars.

·         Stainless Steel Products – All steel alloys are actually made from iron and carbon. The carbon prevents the iron from oxidizing. Chromium and Nickel are added as well to produce stainless steel. There are four classes of alloy steel: structural steels, magnetic alloys, tool and die steels, and heat-resisting stainless steel. Consumers are very familiar with the last type since refrigerators, sinks, forks, knives, and my other products are made from stainless steel.

·         Gold Alloys – Many different types of jewellery that’s ‘gold’ isn’t actually pure gold, but actually an alloy. That’s because gold is incredibly malleable, making it next to impossible to form durable jewellery with. Gold itself is used in manufacturing electronics due to the same malleability and because it is electrically conductive.

 

Chemical Reactions of Alloys –

·         A chemical reaction between Au25 and Ag44 in solution will give rise to alloys of AgAu and AuAg composition. The reaction can be represented as:

Au25 + Ag44 → AgAu24 + AuAg43

Alloy Examples –

Examples of alloys include stainless steel, brass, bronze, white gold, 18k gold, and sterling silver. Although exceptions exist, most alloys are named for their primary or base metal, with an indication of other elements in order of mass percent.

 

·         Stainless Steel: Iron alloy, which typically contains chromium, nickel, and other elements to resist rust or corrosion.

·         Steel: The name given to an alloy of iron with carbon, usually with other elements, such as nickel and cobalt. The other elements add a desired quality to the steel, such as hardness or tensile strength.

·         Brass: a mixture of copper with zinc and sometimes other elements. Brass is hard and durable, making it suitable for plumbing fixtures and machined parts.

·         Bronze: is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon. These additions produce a range of alloys that may be harder than copper alone, or have other useful properties, such as stiffness, ductility, or machinability.

·         18k Gold: this is 75% gold. The other elements typically include copper, nickel, or zinc. This alloy retains the colour and lustre of pure gold, yet is harder and stronger, making it better suited for jewellery.

·         Sterling Silver: is 92.5% silver with copper and other metals. Alloying silver makes it harder and more durable, although the copper tends to lead to greenish-black oxidation (tarnish).

·         Electrum: Some alloys, like electrum, occur naturally. This alloy of silver and gold was highly prized by ancient man.

·         Meteoritic Iron: While meteorites may consist of any number of materials, some are natural alloys of iron and nickel, with extra-terrestrial origins. These alloys were used by ancient cultures to make weapons and tools.

·         Amalgams: These are mercury alloys. The mercury makes the alloy much like a paste. Amalgams may be used in dental fillings, with the mercury intact, although another use is to spread the amalgam and then heat it to vaporize the mercury, leaving a coating of another metal.

·         Pewter: an alloy of tin, with other elements such as copper, lead, or antimony. The alloy is malleable, yet stronger than pure tin, plus it resists the phase change of tin that can make it crumble at low temperatures.

 

Common Alloys and their Applications –

Alloy	Composition	Applications
Babbitt Metal	Tin: 90%, Antimony: 7%, & Copper: 3%	Used in bearings due to its low measure of friction with steel
Bell Metal	Copper: 77% & Tin: 23%	Casting of bells
Brass	Mainly Copper with up to 50% Zinc	Inexpensive Jewellery, hose nozzles & couplings
Bronze	Mainly Copper with up to 12% Tin	Coins & medals, heavy gears, tools electrical hardware
Coin Metal		Used in USA for making coins
Duralumin	Aluminium: 95%, Copper: 4%, Manganese < 1%, Magnesium: 0.5%	Aircraft, boats, railroad cars, and machinery because of its high strength and resistance to corrosion
Gun Metal	Copper: 85 – 90%, Tin: 8 – 12% & Zinc: 1 – 3%
Monel	Nickel: 60%, Copper: 33% & Iron: 7%	Corrosion-resistant containers
Phosphor Bronze	Bronze with a small amount of phosphorus	Springs & boat propellers
Solder Metal	Lead: 50% & Tin: 50%	Joining two metal to each other
Sterling Silver	Silver: 92.5% & Copper: 7.5%	Jewellery & art objects
Type Metal	Lead: 75-95%, Antimony: 2-18% & Tin in trace quantities	Used to make type characters for printing, also used to make decorative objects like statuettes and candlesticks

 

Composite Material –

·         A composite material is a combination of two materials with different physical and chemical properties.

·         When they are combined they create a material which is specialized to do a certain job, for instance to become stronger, lighter or resistant to electricity. They can also improve strength and stiffness. 

·         The reason for their use over traditional materials is because they improve the properties of their base materials and are applicable in many situations.

 

History of Composite Material –

·         In 3400 B.C the first composites were engineered by the Mesopotamians in Iraq.

·         Following this, in around 2181 B.C the Egyptians started to make death masks out of linen or papyrus soaked in plaster.

·         In 1200 A.D, the Mongols began to engineer composite bows which were incredibly effective at the time.

·         In the 1900s this new-found knowledge about chemicals led to the creation of various plastics such as polyester, phenolic and vinyl.

·         The 1930s was an incredibly important time for the advancement of composites. Glass fibre was introduced by Owens Corning who also started the first fibre reinforced polymer (FRP) industry.

·         The composites on a Boeing 787 Dreamliner in the mid-2000s substantiated their use for high strength applications.

 

 

 

 

 

 

Types of Composite Material –

Some common composite materials include:

• Ceramic matrix composite: Ceramic spread out in a ceramic matrix. These are better than normal ceramics as they are thermal shock and fracture resistant.
• Metal matrix composite: A metal spread throughout a matrix.
• Reinforced concrete: Concrete strengthened by a material with high tensile strength such as steel reinforcing bars.
• Glass fibre reinforced concrete: Concrete which is poured into a glass fibre structure with high zirconia content.
• Translucent concrete: Concrete which encases optic fibres.
• Engineered wood: Manufactured wood combined with other cheap materials. One example would be particle board. A specialty material like veneer can also be found in this composite.
• Plywood: Engineered wood by gluing many thin layers of wood together at different angles.
• Engineered bamboo: Strips of bamboo fibre glued together to make a board. This is a useful composite due to the fact it has higher compressive, tensile and flexural strength than wood.
• Parquetry: A square of many wood pieces put together often out of hardwood. It is sold as a decorative piece.
• Wood-plastic composite: Either wood fibre or flour cast in plastic.
• Cement-bonded wood fibre: Mineralized wood pieces cast in cement. This composite has insulating and acoustic properties.
• Fiberglass: Glass fibre combined with a plastic which is relatively inexpensive and flexible.
• Carbon Fibre reinforced polymer: Carbon fibre set in plastic which has a high strength-to-weight ratio.
• Sandwich panel: A variety of composites that are layered on top of each other.
• Composite honeycomb: A selection of composites in many hexagons to form a honeycomb shape.
• Papier-Mache: Paper bound with an adhesive. These are found in crafts.
• Plastic coated paper: Paper coated with plastic to improve durability. An example of where this is used is in playing cards.
• Syntactic foams: Light materials created by filling metals, ceramics or plastics with micro balloons. These balloons are made using either glass, carbon or plastic.

 

Advantages of Composite Material –

·         Low costs compared to metals

·         Design Flexibility

·         Resistance to a wide range of chemical agents

·         Low Weight

·         Durability

·         Electric Insulation

·         High impact strength

Why use Composites?

·         Weight saving is one of the main reasons for using composite materials rather than conventional materials for components. While composites are lighter they can also be stronger than other materials, for example, reinforced carbon-fibre can be up to five times stronger than 1020 grade steel and only one fifth of the weight, making it perfect for structural purposes.

·         Another advantage of using a composite over a conventional type of material is the thermal and chemical resistance as well as the electrical insulation properties. Unlike conventional materials, composites can have multiple properties not often found in a single material.

·         Fibre reinforced composites, such as fibre reinforced plastic (FRP composites), are finding increasing use in the design and manufacture of final products for commercialization.

 

Examples of Composite Uses –

• Electrical equipment
• Aerospace structures
• Infrastructure
• Pipes and tanks
• Homes can be framed using plastic laminated beams